What does French word sacrebleu mean?

"Sacred blue" is a literal English equivalent of the French phrase sacrebleu.

Specifically, the Word combines the adjectives sacre ("sacred") and bleu ("blue"). The phrase nevertheless functions somewhat as a curse which translates more politely as "my God!" or "zounds!" It references the "sacred blue" dress of Mary, mother of Jesus of Nazareth (ca. 7-2 B.C.-A.D. 30-36).